A number of prior art systems exist for applying labels to containers. These systems employ either continuous roll fed labels or cut and stack labels.
Prior art labeling apparatus and methods employing labels in continuous roll form include label cutting and registration means for severing discrete labels from the roll and then registering them for attachment to the containers through a vacuum transfer drive system. In these prior art systems a hot melt adhesive generally is employed; being applied to both the leading and trailing edge of the back side of the labels for permitting attachment of the labels to the containers.
Although the above-described system is being commercially utilized, it does include a number of drawbacks for various applications. First, continuous roll fed labeling systems require both label cutting and registration units, which increase the complexity of the system. Second, hot melt adhesives are, at best, generally cloudy or milky in appearance and therefore are not effectively utilized to apply clear or transparent labels in a uniform fashion to clear containers. The uniform attachment of clear or transparent labels to clear containers, e.g., clear glass or plastic beer and soda bottles, is very desirable, providing a very clean finish, and also permitting the product inside of the bottle to be clearly and easily viewed through the label. A further deficiency in connection with the use of hot melt adhesives is that they generally are difficult to apply as a smooth, continuous layer to the label stock.
It is known to employ continuous rolls of transparent pressure sensitive labels for application to clear containers. However, as discussed above, the use of these continuous rolls require cutting and registration units that increase the complexity of the system. Moreover, the rolls of pressure sensitive labels often include a release liner covering the adhesive surface, thereby necessitating the removal of the release liner from the label during the continuous process. This also introduces an undesired complexity and cost into the system.
It also is known to apply sheet fed/cut and stack labels (i.e., labels that have been cut off line and are retained in a stack within a dispensing magazine) to containers, such as bottles, in a continuous label application system. These latter prior art systems often employ a cold glue adhesive, which is water soluble, and sometimes employ a hot melt adhesive. When a cold glue adhesive is employed it is applied to a glue transfer pad by a transfer roll that commonly is made of steel, and then the glue transfer pad is moved into contact with the lower label of the stack to both apply the glue to that label and remove the label from the stack through surface adhesion between the label and the adhesive. Thereafter, the label, with the cold glue adhesive thereon, is moved to a transfer drum, from where it is then applied to a container, such as a glass bottle. These cold glue adhesives generally have been utilized only in connection with paper labels that are capable of absorbing the moisture from the water soluble adhesives. In other words, systems employing water soluble cold glue adhesives are not well suited for use with non-porous, plastic labels. Although hot melt adhesives also have been employed with cut and stack labels, they are subject to the same deficiencies discussed above with respect to the use of such adhesives on continuous label stock.
Based on the deficiencies of the existing prior art systems, a need exists for a labeling apparatus and method that is not required to handle an excessively tacky adhesive throughout the label handling and applying operations, and that is effective for use with plastic labels for adhering such labels to containers. Although the desired systems of this invention are usable with both opaque and clear plastic labels to adhere such plastic labels to both opaque and clear containers, the most significant need exists in providing a system for adhering clear plastic labels to clear containers, such as clear glass bottles, e.g., beer or soda bottles, without the presence of unsightly striations or other unsightly imperfections in the adhesive distribution. Most preferably a need exists for the aforementioned type of system that does not require the use of label cutting and registration units of the type generally employed in labeling apparatus and methods that handle continuous roll fed labels.